As is generally well known in the prior art, diaphragms are an integral part of pumps and other pneumatic pressure devices. It is necessary in these applications for these diaphragms to remain flexible in order for them to perform their function. However, the constant flexing of the diaphragm when the device is in use causes wear on the parts of the diaphragm that are in contact or attached to non flexing portions of the device.
These nonflexing parts may be the flange, follower and pump housing in the case of pump diaphragms or they could be body housing and piston housing in the case where diaphragms are used in some pneumatic valves. Regardless of its use or whatever is used to secure it, a diaphragm is subject to severe wear because portions of the diaphragm are secured and do not flex while other portions are constantly flexing when in use. It is the area of the diaphragm between the nonflexing portions, known as the "working length", that will exhibit wear and after a time may crack and/or have holes wear through the diaphragm.
When the diaphragm cracks and/or has holes worn through, the device of which the diaphragm is an integral part will be out of operation until a new diaphragm can be installed.
Diaphragms are generally made of an elastomeric material, such as rubber, and may be reinforced by having an inner layer of a fabric material molded between elastomer layers. The fabric layer imparts greater strength to the diaphragm without sacrificing flexibility and therefore permits a diaphragm to be subjected to higher pressures than if it were made solely of rubber, or another elastomer, of the same thickness. Rephrasing the previous sentence, the use of fabric reinforced rubber permits the use of thinner diaphragms which still have the ability to achieve results similar to those obtained through the use of thicker all rubber diaphragms. Thinner diaphragms are preferred for many reasons, including better responsiveness at low temperatures, provided they can still perform the desired function. However, problems have been encountered with fabric reinforced diaphragms in that it has been found that the fabric was not always centered in the diaphragm cross section. This has resulted in premature failure of the diaphragm.
Also in prior art, diaphragms used in diaphragm actuated pistons have employed either a uniform thickness or a gradual taper thickness in the flexing portion of the diaphragm. Stresses resulting from constant flexing have in many cases resulted in compression set wrinkles or kinks in the diaphragm at the flexure points. Such diaphragms have been a trade off in that the diaphragm had to be thick enough to avoid the kinking that can occur easily if the diaphragm is too thin and yet keep the diaphragm thin enough to avoid the creases or wrinkles which can occur in thicker diaphragms. Each of these problems can result in premature failure of the diaphragm.
In all cases, failure of a diaphragm results in "down time" for whatever device it is that uses such diaphragm coupled with the maintenance required to replace the diaphragm. Thus, any modification which can result in longer diaphragm life or improved diaphragm performance, which usually results in longer life, is a welcome improvement.